ELECTROLOCATION Geoff Derven / Wren Kominos-Marvell / Frank Sosa Reed College Bio342

(a) HOW DO BG KNIFEFISH USE AN ELECTRIC ORGAN TO LOCATE FOOD IN THEIR ENVIRONMENT?

BLACK albifrons

• Objects with impedances that differ from the water cast ‘images’ on the ’s skin [1].

• Habituation and Dishabituation occur in [2].

• Electric fish are able to sense the electrical conductivity of objects [3]. fish tank (with food path installed) LEARNING PATHWAYS

Hypothesis: The BG Knifefish will use electrolocation to associate metal cubes with the presence of food.

METAL CUBES ALTER THE UMWELT OF BG KNIFEFISH (b)

• 3 BG Knifefish placed behind starting gates in 3 separate tanks

• Tanks contain pathways of plastic and metal cubes with food located at end of paths.

• BG Knifefish released, timed for successfully locating food.

• Repeated trials run with continuous behavioral sampling.

• Once food-path learned, cubes were reversed, altering electrical field. Trials run again.

overhead view of tank pathway model NAVIGATION & METAL CUES

There was clear evidence of path learning, but no significant difference was found in switching the cube path. One BG Knifefish was observed to be much faster at finding the food after the path was reversed, while another BG Knifefish took much longer. These results point to the possibility of other sensory means as a factor in BG Knifefish navigation.

40

35 Figure 1:

30 Control fish

25 demonstrate Fish1 20 Fish2 decreased Fish3 Time (min) 15 foraging time

10 between initial

5 and final trials.

0 (P=0.1153) 1 2 Initial vs Final

Figure 2: 12

Learned fish 10 do not demonstrate 8 increased Fish1 6 Fish2 Fish3 foraging time Time (min) with respect to 4 reversed cube 2 path. 0 (P=0.350) 1 2 Cube Path UMWELT & BEHAVIORISM BG Knifefish do not navigate their environment exclusively based on presence of metal.

The Black Ghost Knifefish in this experiment have shown to have quick associative learning in both pavlovian and operant conditioning. More work should go into analyzing the limitations and benefits of this electric sense through learning theory. This model organism will be a useful example to demonstrate that principles of learning in-fact generalize across all species. More experimentation in this area will show how the ‘umwelt’ of this organism interacts with learning theory.

REFERENCES [1] Heiligenberg, (1977); Hopkins, 1983a; Zakon, (1983) [2] De Fazio (1979) [3] Hans Lissman and Machin (1958)

IMAGES (a) http://www.recipeapart.com/black-ghost-knife-fish/ (b) http://fishindex.blogspot.com/2008/07/black-ghost-knifefish.html

ACKNOWLEDGMENTS Thanks to… Peter Moller, for his book on electric fish and his comments on our experiment; Suzy Renn, for teaching us about and buying us fish; Kelsey Wood, for her dedicated assistance in the lab; and of course all of our peers in Bio 342.